1. Field of the Invention
The present invention relates to a lens frame supporting mechanism, and more particularly, a lens frame supporting mechanism capable of driving a lens frame, which holds an optical system, in the direction of the optical axis of the optical system.
2. Description of the Related Art
In the past, a lens frame supporting mechanism having a so-called gimbal structure has been employed as a lens frame supporting mechanism that is usable for hand tremor compensation or lock-on control in a camera or the like, and capable of rotating a lens frame in the direction of the optical axis.
FIG. 105 is an oblique view showing a conventional lens frame supporting mechanism using the gimbal structure. A lens barrel 501 that is a lens frame is supported by a first support 502 via a support pin 501a so that the lens barrel 501 can rotate freely. The first support 502 is supported by a second support 503 via a support pin 502a so that the first support 502 can rotate freely. The second support 503 is fixed to and supported by a camera body that is not shown. The lens barrel 501 in the supporting mechanism having the above structure is held in a state in which the lens barrel 501 is disabled from rotating about an optical axis O; that is, restrained from rolling, but enabled to rotate in a vertical direction .theta.y and a horizontal direction .theta.x.
As for rotational drive exerted by the conventional lens frame supporting mechanism having the foregoing structure, in general, when driven by an actuator, which is not shown, mounted on the first support 502, the lens frame supporting mechanism rotates in the vertical direction .theta.y or about the horizontal axis. When driven by an actuator, which is not shown, mounted on the second support 503 or a camera body, the lens frame supporting mechanism rotates in the horizontal direction .theta.x, i.e. about the vertical axis.
In the aforesaid lens frame supporting mechanism, the dual structure consisting of the first and second supports 502 and 503 must be adopted as a supporting mechanism. This makes it inevitable to design a lens barrel which is large in size. Moreover, the actuator responsible for the rotational drive in the vertical rotation .theta.y must be mounted on the first support 502. The first support 502 is supported by the second support 503. The actuator for driving the second support 503 must therefore bear a large load, leading to an increase in power consumption and in size of a lens barrel structure.
A lens frame supporting mechanism adopted for an image blur compensation mechanism, which has been disclosed in Japanese Patent Laid-Open No. 4-104666, uses the gimbal structure shown in FIG. 105. The supporting mechanism is driven bi-directionally by two moving coil actuators that are formed with two energizing coils. The moving coil actuators are installed in a camera body and associated with two magnets fixed to a back end surface 504 of a lens frame that is spherical.
The supporting mechanism shown in FIG. 105 has sway sensors 505a and 505b for detecting a sway in the vertical direction .theta.y and a sway in the horizontal direction .theta.x, respectively. The sway sensors 505a and 505b are supported by the lens barrel 501. When the lens frame supporting mechanism executes image blur compensation, the two moving coil actuators drive the lens barrel 501 so that the sway sensors 505a and 505b will output Os. Thus, image blur compensation is achieved.
In the lens frame supporting mechanism adopted for the image blur compensation mechanism disclosed in the Japanese Patent Laid-Open No. 4-104666, supposing the actuators were mounted outside the supports, one of the aforesaid problems lying in the prior art; that is, a problem that load to the actuator works as a load to the lens barrel would be solved. Nevertheless, because of the supporting structure of the dual structure including the first and second supports 502 and 503, the lens barrel cannot help being designed to be large in size.